Why can't I surf favorite channels

I've chatted with an Xfinity representative, who confirms that Comcast does not make available a method to surf (Channel UP / Channel DOWN) TV viewing, while tuning only to SUBSCRIBED channels, or only to FAVORITE channels. These narrower searches are only available by accessing the GUIDE. Traditional surfing tunes to EVERY station offered by Comcast, EVEN THOSE WHICH ARE NOT AVAILABLE TO THE VIEWER BECAUSE THEY ARE NOT WITHIN HIS/HER SUBSCRIPTION.

Why has Comcast structured viewing in this extremely annoying way (Verizon has had this capability for more than 5 years!)? Is it:

-- To encourage subscribing to more channels (at higher cost)

-- Due to intellectual property limitations?

I would like a real response from Comcast! I encourage viewers to write to Comcast to demand this feature!!